1. Field of the Invention
The present invention relates to a dynamic buffer change system which changes settings for a part of a buffer region divided into a plurality of parts or classes, each of which comprises a plurality of unit buffer areas, and in particular relates to a dynamic buffer change system which dynamically changes settings for the applicable buffer areas of a class in the buffer region upon change request input from a terminal during system operation.
2. Description of the Prior Art
Conventionally, a data base system utilizes a buffer region for temporary data storage in data input/output for the files constituting the data base when provided with a plurality of terminals.
Such a buffer region is usually divided into a plurality of classes for different applications. A class of a buffer area consists of a plurality of unit buffer areas. Data are actually input/output using such buffer areas of each class as units. Buffer areas, which are secured for each class, are conventionally allotted with referring to the initial system setting region which contains the setting for the buffer areas of each class at the time of system activation. In other words, when the system is booted up, it refers to the initial system setting region for each class so that the specified number of buffer areas of specified sizes are secured in the buffer region. These buffer areas for different classes secured in the buffer region are controlled according to the setting contained in the above initial system setting region.
The conventional method to secure buffer areas of the classes as described above merely has buffer areas for the specified number allotted for each class by referring to the initial system setting region when the system is booted up.
The settings for the buffer areas for each class stored in the initial system setting region are set before system activation and cannot be rewritten after starting up of the system. Accordingly, any change in the number or sizes of buffer areas for a class secured in the buffer region will cause a discrepancy between actual arrangement of the buffer areas for the classes and the setting for the buffer areas in the classes given in the initial system setting region, which disables control of the buffer areas in the classes based on the data in the initial system setting region. Thus, it is practically impossible to dynamically change the settings for the buffer areas in the classes.
Specifically, for a conventional system, the setting for the buffer areas of the classes in the buffer region is fixed when the system is started up and such setting cannot be changed. If the necessary class buffer volume changes depending on the task type and time after starting up of the system, the buffer volume may be insufficient for a class used for a task but may be in excess for another class used for another task. With such a system, the buffer region cannot be used effectively.